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$30 Micro Forge 


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$30 Micro Forge 

Written By: Len Cullum 


Drill bits (1) 

Drill press (1) 
or hand drill 

Dust mask (1) 
Hacksaw (1) 
Plumber's torch (1) 
Wrenches (1) 


Firebrick (1) 

Threaded rod (2) 
Youa€™ll cut them in half. 

Nut (16) 

These should fit the 7/16" rod but have a 
smaller outer diameter than the 3/8" 

Washers (16) 

Aluminum angle (1) 

Aluminum plate (2) 
Cut to this size. 

Finishing nails (3) 


I am a woodworker by trade and spend my days building Japanese-style architectural 
elements and structures. Because of my chosen niche, I occasionally need a piece of 
hardware that's impossible to find in this country. Sometimes I ask friends in Japan to track 
it down. But other times, if the piece isn't too complicated, I'll make it myself. Recently, I 
needed to make 500 old-style Japanese nails. In the past I would simply fire up a propane 
plumber's torch, hold each piece over it until it was glowing, and then hammer away. That 
was fine when a dozen nails were all I needed, but this time I knew I needed a more efficient 
way to heat all those nails, so I built a micro forge. 

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$30 Micro Forge 

Note: Firebricks are really soft and easy to cut. So soft, in fact, that you can dig 
into them with a fingernail, but they are still rated to 2,300° F. Ordinary wood/metal 
drill bits go through them like butter. 

The nails I was making were 2V2" long, and I wanted to keep the forge chamber as 
compact as possible, so I used the brick's biggest face (4 1 /2"x9") as the front, which allows 
for the shallowest chamber. Make a mark on the front face, 2 1 /4" in from one end, and 
centered 2 1 /4" from either side. 

Wear a dust mask. Set the drill press to its lowest speed (mine was 250rpm) and drill a 
hole 2 1/8" wide and 2" deep, centered on your mark. 

Note: Drill slowly — you don't want this stuff flying all over the place. With a slow 
speed, most of the dust should stay in the hole until you dump it out. 

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$30 Micro Forge 

Locate and drill the W flame hole, which comes in from the side. I chose to locate it at the 
top of the forge chamber so that the curved sides would cause the flame to circulate, 
hopefully heating everything inside more evenly. I tried to drill this hole to match the angle 
of the torch tip. 

The last step is to drill the small vent hole in the back. I made this hole at the bottom of the 
chamber at an angle in order to coax more convection from the flame. 

• Note: My first micro forge 
attempt was just the 
firebrick with the holes in it. This 
worked great for about a minute, 
then the heat caused the brick to 
crack and start to open like a clam 
It needed a frame. 

• Because I wanted to make it fast 
and simple (and my welding skills 
are a bit rusty) I decided to use off- 
the-shelf parts that could be easily 
cut. Start by cutting the 1" 
aluminum angle into four 4" 

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$30 Micro Forge 

Align a piece on the 4" edge of the aluminum plate and stand the brick against it. 

Place a second angle piece on the other side of the brick and mark the plate along the 
angle's edge. Then clamp the 2 plates together and cut them to size along the line. Cut the 
threaded rods in half and file or grind the cut ends to remove any burrs. 

Now you'll need to lay out the corner holes that will accommodate the 4 threaded rods. To 
assure a proper fit, place a washer in each corner and trace the hole. Then clamp the 
angle to the plate and drill a V2" hole in each corner. 

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$30 Micro Forge 

• At this point you need to find the 
height of your torch tip. Measure 
from the bottom of the tip to the 
bottom of the tank, then subtract 
the height of the flame hole. The 
remainder is your leg length. 

• Thread a nut onto each of the 4 
rods to the leg length, then add a 
washer. Slip the short end of the 
rods through the angles and plate : 
then add another washer and nut. 

• Note: Don't wrench-tighten 
yet because you'll need to 
adjust everything for height and 
make sure it's level once it's all 

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$30 Micro Forge 

Stand it up and add the brick. Adjust the angles so that they fit snugly against the brick 
without crushing it. Stand the torch next to it and make sure the flame hole and tip are 
ined up. 

• When everything is sitting right, spin 4 more nuts and then washers on until they're just 
below the top of the brick. Add the other 2 angles and the top plate, with washers and nuts. 

• Carefully hand-tighten the upper hardware so that everything is holding the brick without 
putting too much pressure anywhere. Wrench-tighten everything. 

• Finally, add the grate that the parts rest on while heating. To keep it simple, I used three 
16d finish nails. I cut their heads and points off, to a length of about 2 1/16", put them in 
the forge chamber, and gave them light downward taps to seat them in place. This made a 
grate low enough to allow me room for moving things in and out, and wide enough to hold 4 
nails at a time. 

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$30 Micro Forge 

• You're ready to fire it up! Place 
your micro forge and torch on a flat 
surface separate from the one 
you'll be pounding on, light the fire, 
and watch it make your metal glow. 

• As of this writing, I've made more 
than 1,000 nails in this little forge 
and it's still going strong. The only 
change I might make would be to 
add all-thread connector nuts as 
feet. I've discovered that propane 
tanks vary in height a bit, and the 
addition of feet would make it 
easier to adjust the height of the 

This project first appeared in MAKE Volume 18 . 

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Weekend Project: Micro Forge PDF 

This document was last generated on 201 3-01 -24 09:30:51 AM. 

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